Anhydrous hydrogen fluoride is widely used as a catalyst in the petrochemical industry. It is particularly effective as an alkylation catalyst, such as in the production of high octane gasoline via the isobutane-isobutylene alkylation reaction. This technology has achieved significant application in refineries. At the same time, because of the volatility of hydrogen fluoride (bp. 19.6.degree. C.), the environmental danger in case of accidental release from industrial reactors or storage tanks to the atmosphere is increasingly unacceptable. To solve this problem, industry has mostly reverted either to the use of sulfuric acid, a less suitable alkylation catalyst which, however, is nonvolatile under most operating conditions, or has operated in a manner which decreases or minimizes the volatility of the hydrogen fluoride catalyst systems.
Certain polyhydrogen fluoride complexes, such as those of pyridine, are known and used as fluorinating agents. Anhydrous hydrogen fluoride in the presence of pyridine has been used for fluorinating steroids (R. R. Hirschmann et al., J. Am. Chem. Soc. 78, 1956, p. 4956). The 30% pyridine-70% hydrogen fluoride system was found to be particularly useful for this reaction (C. G. Bergstrom et al., J. Org. Chem. 28, 1963, p. 2633) and subsequently was developed by Olah et al., J. Org. Chem. 44, 1979, p. 3872 and references cited therein). The use of the reagent for a wide variety of fluorination reactions has been explored. The PPHF reagent and subsequently developed related reagents (T. Fukuhara, et al., Nippon Kagaku Kaish, 1985, p. 1951) were only recognized as convenient fluorinating agents. These reagents have not been previously utilized as alkylation catalysts.